1. Field of the Invention
The present invention relates generally to a connectivity hub, such as a Universal Serial Bus (“USB”) hub, and more particularly to a first connectivity hub with a selectively removable second connectivity hub that interconnects with the first connectivity hub.
2. Description of Related Art
In many applications, it is advantageous to interconnect a single computer port to multiple peripheral devices. A connectivity hub provides a convenient central data connection point for attaching multiple peripheral devices to a computer. The hub relays data from the computer to all enabled devices connected to the data hub, and relays data from the enabled devices to the computer. This data relay can be performed without any data storage or significant delay. The connectivity hub can be connected to the computer via a single upstream connector. The connectivity hub can include a plurality of downstream ports for connecting the peripheral devices to the hub. Some common examples of connectivity hubs include FireWire hubs and USB hubs. Both Firewire hubs and USB hubs utilize standardized connectors at the upstream and downstream ports to provide universal connectivity between peripheral devices and the computer, thus simplifying these connections.
Many connectivity hubs receive power for low power applications via a positive voltage conductor and a ground conductor from a source, such as a computer, through the upstream port. Conventional connectivity hubs can be equipped with a connector for connecting with a transformer plugged into a typical AC outlet for providing DC power to the hub for high-power applications.
One example of a connectivity hub is a USB hub. The USB standard is a communication interface standard that enables data transmission/reception between a single USB host and a plurality of USB devices. USB standard compliant interfaces have been widely used as a communication interface that mainly defines a PC as the USB host and its peripheral devices as the USB devices to enable connection between the PC and the peripheral devices. The USB standard adopts a star-shaped logical bus topology in which a single USB host is connected with plural USB devices. The USB 2.0 standard defines three bus transport speeds: a low speed (“LS”) of 1.5 Mbit/s, a full speed (“FS”) of 12 Mbit/s, and a high speed (“HS”) of 480 Mbit/s. Most USB 2.0 hubs are backward compatible to the USB 1.1 standard that includes the LS and FS bus transport speeds.
Connectivity hubs are available in a variety of shapes and sizes with a varying number of ports, commonly ranging from 2 to 7 ports. Small portable hubs often meant to be used with a laptop computer are commonly referred to as “travel hubs” with two to four available bus-powered ports, since most devices used with laptops away from the user's home or office (i.e., when the user is “on the road”) tend to be smaller, low power devices. Often, when a laptop user docks her computer at home or work, she needs a connectivity hub that has more than the two to four bus-powered ports. That is, she is in need of DC-powered ports, as described above. Until now, this meant that the laptop user needed to purchase two hubs, a travel hub and a larger conventional hub to get additional ports with the DC powered port option.
Users can increase the number of connectivity ports available to them for connecting peripheral devices by daisy-chaining hubs together with upstream cables between the hubs. Some hubs are designed to be “stacked” so that a plurality of similar hubs are affixed to each other to form a rigid structure that saves space. Stackable hubs can have integrated upstream and power connectors that mate when the hubs are stacked, thus eliminating some of the cables needed to daisy-chain the hubs. Until now, stackable hub designs required that the hubs being stacked were all the same type of hub with the same number of ports.
In particular, Laptop computers often have only two type “A” USB ports available, and they are commonly located either on the back or side of the laptop computer, and little clearance is provided around the connectors for plugging in travel hubs or larger USB devices designed to be plugged into the USB ports. To reduce the size of travel hubs and the number of cables the user must carry around while traveling, it would be preferable if the travel hub could plug directly into one of the laptop computer's USB ports similar to a USB flash memory drive. A number of such devices with one, two or even three USB ports molded into one rigid molded unit are currently available. Unfortunately, this solution is often not practical without the use of an upstream extension cable, because a conventional hub tends to block the user's access to other cables and devices plugged into the laptop. The use of an extension cable thus defeats many of the benefits of using a single molded hub unit. Thus, many travel hub manufacturers settle for an alternative solution of having an integrated male type “A” USB connector and upstream cable permanently attached to the travel hub. When not in use, the upstream cable can be stored by folding it, coiling it into a bundle, or wrapping it around the circumference of the travel hub. An improved USB hub design that would allow the user to easily connect her travel hub directly to the USB ports on her laptop computer could allow the user to eliminate the requirement of using the upstream cable and the extension cable when a laptop user connects a travel hub to one of her laptop computer's USB ports. Eliminating the need for this upstream cable would save weight and space for the traveling laptop user.
Accordingly, there is a need for a method of stacking a small non-powered travel hub with a larger DC-powered base-station hub that would eliminate interconnecting cables, and save weight and space for the user. Additionally, the ability to convert the travel hub to a DC-powered hub when interconnected would reduce the need for the user to purchase additional USB hubs to stack, thus providing an improvement over currently available stackable hubs.